The spinal column is a highly complex system of bones and connective tissues that provides support for the body and protects the delicate spinal cord and nerves. The spinal column includes a series of vertebral bodies stacked together. An intervertebral disc is positioned between each vertebral body, and these intervertebral discs cushion and dampen compressive forces exerted upon the spinal column.
However, when there is a spinal disorder, procedures are performed to surgically correct and stabilize spinal curvatures or to facilitate spinal fusion. Spinal column disorders include scoliosis, kyphosis, excess lordosis, spondylolisthesis, and other disorders caused by abnormalities, disease or trauma, such as ruptured or slipped discs, degenerative disc disease, fractured vertebra, and the like. Patients that suffer from such conditions usually experience extreme and debilitating pain, as well as diminished nerve function.
Spinal fixation is one surgical technique that may be used to effectively treat the above-described conditions and, in many cases, to relieve pain. Spinal fixation involves the use of spinal implants and/or mechanical immobilization to fuse two or more vertebral bodies of the spinal column. Furthermore, spinal fixation may be used to alter the alignment of adjacent vertebral bodies relative to one another so as to change the overall alignment of the spinal column.
One such spinal fixation technique involves immobilizing the spine using orthopedic stabilizing rods, commonly referred to as spinal rods, which are positioned generally parallel to the spine. Each rod is attached to various vertebra along the length of the spine by way of vertebra engaging spinal implants which may include, but are not limited to, pedicle screws, pedicle hooks, transverse process hooks, sublaminar hooks, etc. The spinal implants commonly include a U-shaped rod receiving channel for receiving the spinal rod therein. Moreover, the rod receiving channel often includes a means for receiving a fastening mechanism, for example, a set screw, a locking screw, or a cam, to subsequently clamp and fix the position of the spinal rod with respect to the spinal implant.
Instruments are commonly used to insert the spinal rod into position in the receiving channel. Surgeons, however, have often encountered considerable difficulty when using these instruments because of problems associated with aligning the spinal rod(s) within the rod receiving channel(s) formed in the head(s) of the spinal implant(s). For example, the heads of the spinal implants may be out of vertical and/or horizontal alignment with one another due to the curvature of the spine or the size and shape of each vertebrae.